The conventional direct-lit backlight module used for a display comprises a plurality LEDs and is directly disposed onto a display panel. The current commercial available LED die bonder and wire bonder have very narrow limitation of the sample holder size, which can only adapt PCB substrate or other substrates no larger than the width equal to 60 mm and the length equal to 250 mm. Therefore, for a final lighting device at A4 size, i.e. 210 mm×300 mm, or larger, a method for the panelization of a multiple PCB substrates becomes necessary. Given the above, a lighting device with a large size lighting panel needs to be developed in this field.